1. Field of the Invention
The present invention relates to apparatus and methods for determining cutting tool dullness by analyzing surface conditions on a workpiece.
2. Description of the Prior Art
In both automatic and manual machine operations, it is important to know the degree of wear or dullness of the cutting tool. Different methods of attempting to monitor cutting tool dullness have been advanced, and tool wear sensors that provide on-line measurements have long been sought after. Some current methods are disclosed in articles entitled, "Measuring Cutting Tool Wear On-Line: Some Practical Considerations", Manufacturing Engineering, July 1984, pages 55-60; and "New Tool-Wear Sensors Aid Adaptive Machining", Tooling and Precision. December 1987, pages 41-43. The methods disclosed in these articles are characterized as being either direct or indirect methods. Indirect methods include force measurement, temperature measurement, vibration measurement, and sound measurement techniques. Present direct methods use workpiece size change, radiometric, tool/work junction electrical resistance and optical monitoring.
Addition art that shows apparatus for monitoring various cutting tool conditions is shown in U.S. Pat. No. 4,644,335 which provides information by way of acoustic signature; Pat. No. 3,889,520 which provides a fluidic system for monitoring machine tool wear resulting in a change in gap between the nozzle and the workpiece as the cutting tool wears; and U.S. Pat. No. 4,563,897 which is based upon a vibration value that is compared to a stored parameter.
The prior art generally is used for detecting breaks in tools which gives sharp spike in output signal. It has been long desired to have an on-line device which was reliable and accurate.
U.S. Pat. No. 4,854,161 shows a method of diagnosing cutting tool dullness which utilizes two known parameters and measures these parameters and then provides values based on the two parameters and characterizes the tool if the known value is greater than the threshold. This, however, does involve making two measurements and comparing the results.